This invention relates to a nickel germanosilicide on SiGe integrated circuit device, and a method of making the same and, more particularly, to a thermally stable nickel germanosilicide on SiGe integrated circuit device, and a method of making the same, wherein during fabrication iridium or cobalt is added at the Ni/SiGe interface to decrease the sheet resistance of the device.
The development of Si-Ge based integrated circuit devices has created the need for stable, low thermal budget, low resistivity metal-silicide contacts to SiGe alloys. Metal/SiGe systems based on titanium, cobalt, zirconium, nickel, palladium and platinum have been studied. However, these systems show poor phase segregation. In particular, during the thermal anneal, in the Ti/SiGe system, excess germanium combines with silicon and nucleates as SiGe precipitates along the grain boundaries. In the Co/SiGe system, excess Ge diffuses to the grain boundary to form Ge-enriched clusters. Due to this multi-phase formation, application of these materials to devices with small feature sizes is difficult unless a silicon buffer layer is used.
Recently, nickel has been applied to poly-silicon germanium (poly-SiGe) to form nickel germanosilicide poly-silicon germanium (Ni(SixGe1xe2x88x92x)/poly-Si0.8Ge0.2) gate structures without a polysilicon buffer layer. Use of this structure has been demonstrated to result in a ten percent increase of the saturated drain current (Idsat) in 0.15 xcexcm pMOSFET. However, the thermal stability of this nickel germanosilicide is very poor. A sharp increase in the sheet resistance is observed at about 600xc2x0 C. Accordingly, there is a need to improve the thermal stability of nickel germanosilicides.
The system of the present invention provides a thermally stable nickel germanosilicide on SiGe integrated circuit device, and a method of making the same, wherein during fabrication iridium or cobalt is added at the Ni/SiGe interface to decrease the sheet resistance of the device. The device comprising nickel silicide with iridium on SiGe shows thermal stability at temperatures up to 800xc2x0 C. The device comprising nickel silicide with cobalt on SiGe shows a decrease in the sheet resistance with temperature, i.e., the resistance remains low when annealing temperatures extend up to and beyond 800xc2x0 C.
Accordingly, an object of the invention is to provide a thermally stable nickel germanosilicide on SiGe integrated circuit device, and a method of making the same.
Another object of the invention is to provide a thermally stable nickel germanosilicide on SiGe integrated circuit device, and a method of making the same, wherein during fabrication iridium or cobalt is added at the Ni/SiGe interface.
Still another object of the invention is to provide a thermally stable nickel germanosilicide on SiGe integrated circuit device that has a low sheet resistance at temperatures up to 800xc2x0 C. or more.